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Can I sell a 1975 Piper Cherokee Archer II with no Logs?
My father had a major stroke and I’m having to sell off his assets to fund his healthcare.  One of the assets is a 1975 Cherokee Archer Piper PA-28-181. Unfortunately, I can’t find his logs/maintenance records. It’s quite frustrating because he was meticulous about keeping records.  The plane hasn’t been in the air in 8+ years. It’s always been hangared.  He overhauled the Lycoming engine 15 years ago but didn’t fly much after that. Maybe 100-200 hours max.  I know there is zero proof of anything without logs. With that said, is there a way to sell it?

Could you let us know where in the world you're based. GdD has given a great answer but focuses on the US. If you're in a different jurisdiction the same general advice applies but with different agencies/organisations.

Lordy, I didn't think to ask @Jamiec!

I realise that planes are significantly different to cars, but can't you arrange to a have 'full service' done?  You may not have that history, but don't flyers really just want a plane that works and has been serviced correctly?  Isn't there a way to do that, without the logs?

To make sure: absolutely no logs are availlable? Flight hours, service/maintenance?

@Neil Pilots are extremely safety conscious for a reason, their lives depend on the correct working of the aircraft. Not knowing when or if the engine has been correctly maintained has direct potentially catastrophic consequences for you operation. In a car you simply pull over, but in an aircraft, you might crash! Additionally, you also might not be able to legally fly you aircraft anymore. A service of the engine alone will costs upwards of 20k$. Therefore yes, logs are important!

@Neil You can. It just costs $$$. Lots of them. A buyer is taking on a lot of financial risk buying an airplane that doesn't have its logs in order.

Thank you all for your advice.  I am based in Richmond, TX.  I will continue looking for the logs and try to locate the outfit that overhauled the engine.  The FAA should have records as well.  Thanks again!

Can you sell it without logs? Of course. You'll just lose a lot of value.

It's definitely worth getting the records figured out, it will make a huge difference to the price and bring many more buyers. Fortunately all is not lost. Maintenance organizations keep records of their work, it's required by regulation for certified airplanes, how long depends on the work done. Some records must be kept for the life of the aircraft or engine. The FAA holds records as well.
Firstly I would ask around the airfield, talk to people and find out what they know. Pilots often love to talk to other pilots as they share the same disease, and owners like to compare notes on maintenance organizations, so you may find a long-time pilot who remembers some details.
Next is to find the maintenance organization which worked on the airplane, and ask them for help. I'd start at the local FBOs, that is fixed base operators at airports that provide maintenance and support services. If you have one or two at the airport that the airplane is based at that would be the place to start, otherwise look at the closest airports that have FBOs as it's unlikely your father went far.
You need to track down what company did the engine overhaul, showing the provenance could double the value of the airplane. There's only so many shops that do a full overhaul, and they have to keep records as well. The maintenance organization again should be able to tell you, or at least narrow it down.
At the same time you can make a records request to the FAA, you could also call your local FAA field office and ask for help. I'm not a legal expert, I suspect as you are not the aircraft's legal owner you'll need to show power of attorney. You waste nothing by trying, it's what they're for. You can also get a replacement registration and other documents.
Before you start it would help you to find the airplane's airframe number and other information from the airplane's data plate, if I remember it's on the airframe down by the pilot's left thigh, which would be in front of the seat on the left side, riveted to the fuselage.
Other countries work similarly, with requirements for maintenance companies to keep records, so I would still approach this the same way, just change FAA to the civil aviation administration/authority of the country the airplane is registered to.
It will likely be a bit of legwork but an investment time and a small amount of money could get you where you need to be. Good hunting!

Logs aren't required to sell it. Just put out an ad saying what you know about it. The sale price will be significantly less, but besides finding the logs there's nothing you can do about that.
Whatever information you can collect will help. You can ask the FAA for records of major alterations and repairs (337 forms), which will include some information like the total airframe time at the time of the repair. If you can track down the mechanics who actually did the work you may be able to get information from them as well.
But you're ultimately still selling an airplane without most of the logs, and one that has been sitting unused for a long time. Either you or the new owner will need to sink a significant amount of time and/or money to make it legal and safe to fly again.
You could get it inspected yourself and get it into airworthy condition before selling it. But this would involve time and money. Potentially a lot of both. It would be all to easy to end up in the red, so I don't recommend this if you need the money.

Well this wasn't very helpful. An aircraft with no documentation might have the scrap value of the metal or less...

@Jpe61 Aircraft get sold without logs all the time. It decreases the sale value to be sure, but not nearly to scrap metal level. All it needs is a new annual inspection (which it would need anyway), along with confirmation that all ADs have been complied with (which is going to be more work without previous records).

That would be very different if (as I understood the question when I read it) if there were zero logs availlable. It would be difficult to track total hours, overhauls, maintenance etc. That's something that can't be shrug off by simple inspection.

@Jpe61 Any ADs that are required to be done every x hours will need to be done immediately. One time ADs may or may not need to be done again depending on the AD. Obviously any new ADs since it was last flown will need to be taken care of. TBOs are advisory to begin with so not knowing exactly how many hours are on the engine is not as big a deal as it might seem. If it's been mostly sitting for 15 years it's likely to need an overhaul before TBO anyway.


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Is it common for aircraft tugs to work from under the aircraft?
I came across this photo showing a tug attached in a way I have never seen before. I assume it was used to allow the aircraft closer to the terminal.
Did this require special equipment or modifications to the aircraft?
Was it a common practice before terminals were redesigned to accommodate large aircraft and large tugs.

Source: wikipedia.org

Man that pic of dear departed Canadian Pacific Airlines a/c is old. Mid 70s.

Seen this done at the old Kuala Lumpur (KUL) airport at Subang. The issue was a lot of stands were designed to take B707s and DC8s. When the 747 came around quite a few had a hard time finding the required space as there were usually buildings in front and taxiways at the rear. In Subang the stand was just in front of the terminal building with just a narrow service road in front. If the pilot was a bit slow to hit the brakes then the tug would not be able to get in front of the nosewheel, thereby requiring the towbar to be positioned behind the nosewheel.

Yes, this is a perfectly normal practice, still used, especially for tight spaces, as seen in this video moving a 747 into the hangar for service. And no, it doesn't require any special equipment - the nose gear attachment is designed to be used either way.
A still from the video:

Are all nose gear designed to be used that way? Is it just a B747 specificity?

While it's uncommon, it appears that many pushback tugs are specifically designed to fit underneath an aircraft like this. This wiki notes that (emphasis mine)

Pushback tractors use a low profile design to fit under the aircraft nose. For sufficient traction, the tractor must be heavy, and most models can have extra ballast added. A typical tractor for large aircraft weighs up to 54 t (120,000 lb) and has a drawbar pull of 334 kN (75,000 lbf).1 Often, the driver's cabin can be raised for increased visibility when reversing, and lowered to fit under aircraft.

This modern aircraft tug is shown next to a 747

You can see it fits underneath entirely once the cab is lowered. Since many aircraft have a clearance height similar to the 747, it likely can fit under most large-body aircraft.

Often, the driver's cabin can be raised for increased visibility when reversing, and lowered to fit under aircraft - that sounds risky, have there ever been any cases where that caused damage to the plane when the operator forgot to lower it before moving under the plane, or accidentally raised it while under the plane?

I worked, as a pilot on the 747, for CPAir, and that was a common method used to push us back.  We drove into the gate under our own power.

Welcome to Av.SE! Thanks for adding first-hand perspective to this thread. Please come back often!

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

sort: votes


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How long can a commercial airliner fly at 90deg roll?
For how long can a commercial airliner fly at a 90deg roll angle ? Or can it at all ?

Depends on what you consider to qualify as flying. Does it have to stay at the same flight level? (spoiler: it won't) Or are you interested in the sink rate in this attitude?

FWIW, I don't think this is primarily opinion-based. Data may be hard to come by, because few people are likely to be crazy enough to pull a stunt like that (and even fewer are likely to be in a position of being able and willing to allow people to pull the stunt), but that just makes the question difficult to answer, it doesn't mean that answers cannot be based in fact. That said, as AEhere pointed out, an [Edit] to clarify what constitutes "flying" in this context would likely help answerability.

As others have noted, it is important that you specify whether you are requiring that the altitude remain constant, or not.  An arcing parabolic maneuver is much different from a constant-altitude maneuver, i.e. true knife-edge flight.

(The smart*** answer is: "until it hits the ground" --  )

There is no need to close this question. It is a question based on the physics of flight, not upon the opinion of a random commentator. There are really good answers posted, with multiple upvotes.

Look up videos for "Fairchild AFB B-52 crash" on youtube for an example of a B-52 in knife-edge flight one wing span off the ground. it does not end well.

What you're talking about is called "knife edge" flight, where all of the lift is coming from the sideways fuselage, making it a lifting body aircraft with big fins (the wings) sticking up and down that aren't doing anything (rolling sideways during a ballistic arc doesn't count).   The rudder is doing the job of the elevator, and the elevator is doing the job of the rudder.
To do this is requires a fairly deep fuselage profile, preferably reasonably flat sided so it makes a decent lifting body, with a really powerful rudder to effectively function as the elevator for this lifting body, and it's helpful to have a high power propeller engine on the nose helping with the lift generation.
Just about the only airplanes that meet those characteristics are purpose built aerobatic machines that can sustain knife edge flight indefinitely or some military jets.  Certainly no airliner could ever do that.

Boeing considers 90 degree bank to be an out of control event, and this paper discusses methods to recover.
https://www.boeing.com/commercial/aeromagazine/aero_03/textonly/fo01txt.html

HIGH BANK ANGLES.
  A high bank angle is one beyond that necessary for normal flight. Though the bank angle for an upset has been defined as unintentionally more than 45 degrees, it is possible to experience bank angles greater than 90 degrees.
Any time the airplane is not in "zero-angle-of-bank" flight, lift created by the wings is not being fully applied against gravity, and more than 1 g will be required for level flight (figure 6). At bank angles greater than 67 degrees, level flight cannot be maintained within flight manual limits for a 2.5 g load factor (figure 7). In high bank angle increasing airspeed situations, the primary objective is to maneuver the lift of the airplane to directly oppose the force of gravity by rolling to wings level. Applying nose-up elevator at bank angles above 60 degrees causes no appreciable change in pitch attitude and may exceed normal structure load limits as well as the wing angle of attack for stall. The closer the lift vector is to vertical (wings level), the more effective the applied g is in recovering the airplane.
A smooth application of up to full lateral control should provide enough roll control power to establish a very positive recovery roll rate. If full roll control application is not satisfactory, it may even be necessary to apply some rudder in the direction of the desired roll.
Only a small amount of rudder is needed. Too much rudder applied too quickly or held too long may result in loss of lateral and directional control or structural failure.
NOSE HIGH, HIGH BANK ANGLES.
  A nose-high, high-angle-of-bank upset requires deliberate flight control inputs. A large bank angle is helpful in reducing excessively high pitch attitudes. The pilot must apply nose-down elevator and adjust the bank angle to achieve the desired rate of pitch reduction while considering energy management. Once the pitch attitude has been reduced to the desired level, it is necessary only to reduce the bank angle, ensure that sufficient airspeed has been achieved, and return the airplane to level flight.
NOSE LOW, HIGH BANK ANGLES.
  The nose-low, high-angle-of-bank upset requires prompt action by the pilot as potential energy (altitude) is rapidly being exchanged for kinetic energy (airspeed). Even if the airplane is at a high enough altitude that ground impact is not an immediate concern, airspeed can rapidly increase beyond airplane design limits. Simultaneous application of roll and adjustment of thrust may be necessary. It may be necessary to apply nose-down elevator to limit the amount of lift, which will be acting toward the ground if the bank angle exceeds 90 degrees. This will also reduce wing angle of attack to improve roll capability. Full aileron and spoiler input should be used if necessary to smoothly establish a recovery roll rate toward the nearest horizon. It is important to not increase g force or use nose-up elevator or stabilizer until approaching wings level. The pilot should also extend the speed brakes as necessary.

A commercial airliner will not support sustained coordinated flight with a 90 degree roll attitude.  This is because the vertical lift at 90 degrees is less than the aircraft's weight (and, therefore, the lift needed to support the aircraft).
In general, aircraft with can perform sustained flight in a 90 degree roll attitude will have either some way of creating lift in that direction or will use thrust vectoring or both.  Commercial airliners do not have these attributes. Actually very few airplanes do.
So in the case of a commercial airliner, in a 90 degree roll, one can expect that it will be "falling" towards the ground, with increasing velocity as it accelerates. This is because it generates insufficient vertical lift in that flight attitude.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


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Is it possible to hack an airplane while it's moving (in general)?
I recently searching Airbus Careers section, and I can say that I saw too many Cyber Security job positions. It was saying in the job description that there is a need of having knowledge about avionics and of other related sections. It was not focusing on Computer Science part.
My question is this: Is there a way that someone can hack an airplane? I mean each airplane is moving. How can someone "touch" a moving airplane, have the time to identify it and then to hack it?
Also, the airports are having really specialized machines and systems in order to communicate with an airplane. How can someone, without having specialized machines, can hack an airplane?

Possible duplicate of Can a Boeing 777 be hacked?

It would depend on the type of airplane, wouldn't it?  I very much doubt my 1960s vintage Cherokee could be hacked :-)

The answer to

Is it possible to hack an airplane while it's moving?

is "theoretically yes, movement has no effect on a plane hackability".

How can someone "touch" a moving airplane, have the time to identify it and then to hack it?

All the people inside the airplane are touching it during the whole flight, they know which airplane they are flying with, and they have a flight worth of time.

How can someone, without having specialized machines, can hack an airplane?

Theoretically, for some components, you don't need specialized machines (see below), you need a laptop and an ethernet cable
see here (TL;DR version ), or here, and finally, from here

First, the airplanes. The problem the GAO identifies is one computer security experts have talked about for years. Newer planes such as the Boeing 787 Dreamliner and the Airbus A350 and A380 have a single network that is used both by pilots to fly the plane and passengers for their Wi-Fi connections. The risk is that a hacker sitting in the back of the plane, or even one on the ground, could use the Wi-Fi connection to hack into the avionics and then remotely fly the plane.
The report doesn't explain how someone could do this, and there are currently no known vulnerabilities that a hacker could exploit. But all systems are vulnerable--we simply don't have the engineering expertise to design and build perfectly secure computers and networks--so of course we believe this kind of attack is theoretically possible.

As we read here, though, safety critical components are not that easy to compromise:

it’s essential to understand that aircraft systems can’t be updated in-flight or on the fly. This means that if an attacker is seated on the airplane, there’s no way they could modify systems. There are only three ways to update a system on a modern aircraft:
  1. Take the hardware off the aircraft and return it to the manufacturer for a factory performed update.
  2. Some larger airlines have their own maintenance organizations with the required specialized equipment to perform a bench update of a particular system using a portable data loader (PDL) or some other type of specialized data-loader.
  3. On-wing update [...] Specialized hardware (physical switch(es)) must be set, to place the IMA and relevant systems in maintenance mode. Once the aircraft systems are in maintenance mode, a maintenance engineer needs to follow a sequence of steps to push the update to the target system. The concept of an automatic update does not exist for any safety-critical system.

So, to summarize: yes, researchers have identified non-critical systems that could be hacked (as the passenger entertainment devices), but so far nobody has demonstrated the feasibility of hacking a critical system

Wow. I had no idea. A socking part of an article that you gave me is this: "While we appreciate responsible engagement from independent cybersecurity researchers, we’re disappointed in IOActive’s irresponsible presentation."
Amazing! So yes there is a high possibility to hack an airplane. The thing is that for now there are 0 attempts.
Thanks for your answer. It was more than clear :)

I doubt the planes avionics can be affected as there is typically either an air gap or data verification/validation between systems of differing criticality.

@selectstriker2 - you'd expect that, but it is not always the case. And where there is data verification/validation, it's always possible for the systems to get it badly wrong :-)

"Remember the GAO's nightmare scenario: A hacker on the ground exploits a vulnerability in the airplane's Wi-Fi system to gain access to the airplane's network."  Can a user on the Gnd even get a WiFi connection to something moving over a hundred miles an hour just before landing without being right under the plane (shortest distance)? That's a pretty big stretch.  "A general rule of thumb in home networking says that Wi-Fi routers operating on the traditional 2.4 GHz band reach up to 150 feet (46 m) indoors and 300 feet (92 m) outdoors. "  Planes are >300 feet up until well down the runway.

@CrossRoads: The risk is more like: A passenger uses the plane's onboard Wi-Fi to browse to a rogue web site, which then causes their browser (connected to the plane's Wi-Fi, remember) to do something malicious.

@avionerman, the IOActive's presentation is irresponsible in that it is scaremongering. They admit they don't have the engineering experience to make proper analysis of how dangerous it actually is, and they are missing many steps to get to anything actually dangerous—because the system they got in is not safety critical, so all the serious protections only start behind it—yet present it as imminent danger. But defending against this kind of PR is part of a reason why avionics manufacturers need security experts.

Your last quote seems to contradict your first point.

Even if a hacker can only hack the entertainment devices, the potential damage it can make in conjunction with psychological tactical to create panic in hundreds of passenger is not negligible

While it may be possible for an attacker to get into certain parts of a network - for example, the infotainment system or a crew system, the avionics portion of an aircraft's system is segregated or air-gapped (depending on the aircraft's age / specification) - so, while it may be possible to interact with certain domains of the aircraft's systems there will be difficulty in transitioning from a lower-security domain such as infotainment/crew to a high-security e.g. avionics domain. This was not covered in Ruben Santamara's talk as he didn't have access to the details regarding segregation and the specifications of other parts of the network, he also wasn't working with the most up-to-date version of Boeing's code. - Further, the in-flight wifi system, while vulnerable (weaknesses were highlighted in certain systems whereby routers were discoverable on the Internet and installed with default creds), are not connected to other systems within the aircraft save for power, and as yet (as far as I'm aware) no National Aviation Authority has sanctioned the use of over-the-air updates for avionics or any other aircraft system, and all changes will still be subject to updates with safety cases etc.
Of course, this depends on the manufacturer and air carrier correctly implementing security controls.
It's also worth noting that Airbus' cyber security consultancy does not just focus on aviation, but has many contracts within defence and government.
Edit: Worth noting that larger a/c will be almost completely different in terms of avionics compared to GA which uses the CANBus system also found on road vehicles etc - however, again, physical access would still be needed.

Let's distinguish the two types of "hacking" we're talking about
Total control of the airplane
This is the stuff of Hollywood and is often over-dramatized. The new season of Dr. Who started off with a car being "hacked" and trying to drive itself off a parking deck. If you're not shaking your head, you should be. This wasn't a self-driving car, it was just a regular one (it had a driver before it vaporized him with a laser from the console screen). The idea that most modern cars could be hacked to drive themselves somewhere dangerous is laughable at present. That, and hacking is so wildly overblown that it's noteworthy when someone tries to make a movie or show with realistic intrusions.
Most aircraft have two computers (at least). For simplicity, we'll call the one that controls the aircraft movement the flight control computer. Most airplanes have a way to disengage any other on-board computer and fall back to this device, which takes inputs from the control systems (i.e. the steering yoke). This computer is almost certainly not hackable because they generally don't take any input from the network. If you were going to hack this computer, you would need physical access to the plane, intimate working knowledge of the on-board computers, and a new OS/firmware you could upload into the computers (plus some way to add a way for you to control it remotely).
Messing with your head
A far more realistic scenario is that a hacker gains control of some other subsystem that is hooked to the network and wreaks havoc

In his 2014 research, Santamarta found that an in-flight airline WiFi network was vulnerable to malicious behavior via vulnerable Cobham AVIATOR 700 satellite terminals on the WiFi. The danger there was an attacker gaining control over the Satellite Data Unit or the SwiftBroadband Unit interface by taking advantage of the weak password reset feature, hardcoded credentials, or the insecure protocols in the terminal.
"More specifically, a successful attack could compromise control of the satellite link channel used by the Future Air Navigation System (FANS), Controller Pilot Data Link Communications (CPDLC) or Aircraft Communications Addressing and Reporting System (ACARS)," he wrote in his 2014 research paper. "A malfunction of these subsystems could pose a safety threat for the entire aircraft."

Imagine that ACARS suddenly starts feeding erratic data. Ground stations begin to get notices the engines have shut down or are malfunctioning. The air crew might divert out of an abundance of caution. This is costly for everyone involved, because now you're taking a plane out of service for inspection and having to reroute passengers. Worse, you have a crew potentially no longer trusting on-board systems.
These "soft" intrusions are no less dangerous, but they are very real. Often times, network security is a low priority and anything that touches the network is potentially vulnerable. You can't directly crash a plane, but messing with a crews' head can be just as dangerous.

Yes
At Defcon this year there was an entire Aviation Hacking Village - demonstrating and discussing hack techniques and defences. The village is specifically created to identify vulnerabilities and inform manufacturers of them before they are used in the wild, allowing them to be remediated. See specifically, Harshad's talk at 1030 on Sunday for ILS system attacks, and the various CANbus exploits.

Speaking Schedule:
Friday 9th August – Bally’s Hotel Event Center – Track 1
Time   Talk + Speaker

1300 – 1315 Can the CAN bus fly Risks of CAN bus networks within avionics systems
  Patrick Kiley
1315 – 1400 Behind the scenes of hacking airplanes
  Zoltan and Ben
1400 – 1430 Hacking the Air Force and Beyond
  Dr. Will Roper and Jack Cable
1430 – 1500 A Hacker Walks Into A Flight School And Says Ouch: Common Online Security Fails In Pilot Training
  Tarah

Saturday 10th August – Bally’s Hotel Event Center – Track 1
Time   Talk + Speaker

1000 – 1100 Panel – The Long Haul: The State of Aviation
  Security Policy
  Andrea, Stefan, Pete, Renderman
1100 – 1200 A hackers first solo: airplane avionics security 101
  Ken and Alex

Sunday 11th August – Bally’s Hotel Event Center – Track 1
Time   Talk + Speaker

1000 – 1030 Ideas whose time has come: CVD, SBOM, and SOTA
  Katie and Art
1030 – 1100 Wireless Attacks on Aircraft Instrument Landing System
  Harshad
1100 – 1130 In The Air And On The Air: Aviation Radio Systems
  Exploding Lemur
1130 – 1200 An introduction to the ARINC standards
  Karl

Demos and Show-And-Tell:
Date / Time    Event

All Day / Every Day CANBus Avionics Demo
  Patrick from Rapid 7
All Day / Every Day PTP Workshop
All Day / Every Day Bricks in the Loop
  DDS
All Day / Every Day ADS-B Workshop
  Renderman and Jim   Workshop
Sat 10th / 1100 Talk: A Venture into the Dark Side
  John McCarthy
  Workshop

"Fail" is a verb not a noun.

@quietflyer, "Fail" can certainly be used as a noun these days

Without making a judgement on whether commercial aircraft are vulnerable to hacking, a convention on a topic does not make that topic plausible. For example, see any conspiracy theory conventions. Therefore, I wonder how does this answer the question?

It's not a convention on the topic - that was part of the world's biggest hacking convention, demonstrating attacks, so it absolutely answers the question. Or maybe I should just start with the word- Yes :-)

I haven't heard of anyone demonstrating anything, except in simulators

Well - it's really worth following the links on that page to their twitter, and I think videos. I think there were two valid vulnerabilities over the last couple of years (It's not my field, I'm more critical infrastructure and private sector)

Answers should stand on their own, if something was demonstrated at this convention, you should mention it.

@AEhere - I'm happy to take it to chat, either here or over on security.stackexchange. Please read the list of talk titles above, and be aware that there have been valid (although limited attacks) by ethical hackers already, as noted by Federico. The Defcon ones are new - and thankfully discussed with the manufacturers so they can fix before publication.

@RoryAlsop I don't think I can add much beyond the points I already have raised: this is a list of panels about hacking, that does not imply they come to positive or practical conclusions, if they did have a notable result to show, it should be explicitly linked. As it stands this is a link-only answer where you have quoted the less useful part of the linked content. Contrast with Federico whose answer links directly to the claims and counterclaims, and quotes a specific vulnerability concern.

@AEhere - I disagree, the titles are the key items. As I stated, the talks are about the attacks and defences developed. They do have practical conclusions, which help the industry improve, and I'd suggest it is worth your attention. But you are entitled to your opinion, so have a good day.

I have to agree. This is not an answer. I have read a few of the reports from Defcon this year and they did indeed find some pretty important potential vulnerabilities. But this doesn't detail any of them. Its just a schedule of what various people spoke about, and an invition to go look in another castle.

@RoryAlsop I, in turn, disagree that "An introduction to the ARINC standards" or "Hacking the Air Force and Beyond"  give any meaningful insight into the kind of conclusions one can expect from those panels. Even I could host something that fits under the first one, given some time to brush up, and not mention hacking once. This topic does have my attention, hence my interest in this question; my gripe here is with the way in which your information is presented, which is vague even by aviation hacker claim standards. If they do have practical conclusions, why not link or summarize them?

Because the presentations are not published online yet


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Is Saudia's 777-368ER The Longest Passenger Aircraft?
I watched a video about passenger aircraft length (video was removed from YouTube)
It says the longest passenger aircraft is Saudia's 777-368ER.
Saudia web site says their 777-368ER is 78.86m.
But according to the Boeing web site, 777-300ER is 73.9 m.
Is the 777 be able to made longer as customer option?
I couldn't find any news souce about Saudia purchasing a modified 777.

I wander how two sources can come up with such precise and contradictory figures. It is not as if they tell "it's about 75m"

As far as length is concerned, there are two versions of the 777 classic series, the -200 and -300. The -300 is the longer one, at 242 ft 4 in (73.86 m). Other than choosing one of these two models, there is no customer option to change the length of the plane. I'm not sure where the Saudia data comes from.
But the 777-300 is not the longest plane in the world. The A340-600 previously held that title, at 247 ft 4 in (75.36 m). The 747-8 surpassed this at 250 ft 2 in (76.3 m). The 777-9 may enter service in 2021, setting a new record of 251 ft 9 in (76.7 m).

I thought the A340-600 too was the longest aircraft in commercial production. It's a staggeringly long aircraft!

The Boeing Boeing 777-300 series has a maximum length of 242 ft 4 in (73.86 m).
The Boeing 747-8 has a maximum length of at 250 ft 2 in (76.25 m), making it 8 ft 2 in (2.39 m) longer than the 777.
In comparison, the Airbus A380-800 is 238 ft 7 in (72.72 m) or 12 ft  5in (3.53 m) shorter than the 747-8.


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Could an passenger jet perform a complete power down & up IN FLIGHT?
I've read various references that it is not uncommon that modern passenger jets' computer systems need an occasional reboot to fix some erratic state.
Of course, that is done on the ground and passengers sit a while in the dark before the plane is restarted.
Say an A320, or a 767, or the like would encounter a serious computer problem while at travel altitude. Could a complete reboot of all systems (aka power down and restart the entire plane) be performed while in the air?
Edit:
Topic 27629 already gives some information on the subject, that rebooting a few subsystems is sometimes performed in flight, but some problems require powering down the whole plane.

Which computer systems? For example, an Airbus A350 has six redundant flight computers (three primary, three secondary, each one of them again doubly-redundant), several CPIOMs (each at least doubly-redundant), computers for the in-flight entertainment, passenger information systems, cabin information systems, etc. Each engine has multiply-redundant FADECs. On the A380, there are separate computer systems for the slides and doors. And so on … I would assume, for example, that rebooting a media server in flight would in the worst case lead to an interruption in a movie.

@ManoG1234609 What specifically did you read, and where?

https://aviation.stackexchange.com/q/2072/27629

I cannot remember but there was one accident caused by pilot on and off computer in-flight.

"some problems require powering down the whole plane.". Do you have a reference for this?

There would be no powering down the entire aircraft in flight. No fly-by-wire system could even do this. Computer-wise, it's possible to shut down and restart some of these mostly due to redundancy. @sophit said it well.


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Why does the wing drop prior to a spin?
In the process of understanding the aerodynamics of spins, I'm having a hard time understanding why one wing drops.
I understand that the for spins to occur, a stall + a yaw must occur. I also understand that both wings are stalled, but one is more stalled.
Let's say we're doing stall practice and a student puts in too much right rudder. The nose will swing to the right, causing the left wing to accelerate and the right to decelerate. This will result in more lift on the left and less on the right.
What I'm having trouble understanding is why the right (inner) wing will exceed the critical angle of attack first.
Why does one wing exceed the critical angle of attack further than the other?

Some good discussion happening here: https://www.reddit.com/r/flying/s/rMzBVBy0L1

Think about the free airstream velocity vector of the two wings. Not just the magnitude, (airspeed) of the air, but the relative direction (AOA) of the air molecules when they hit the leading edge. Just like the rotor on a helicoptor, molecules hitting the leading edge of the aft moving wing are impacting the wing at a higher AOA than the ones on the forward moving wing. This is because the velocity vector of the air molecules, relative to the airfoil, must be determined based on the velocity of the aircraft through the airmass, and the velocity of each portion of the wing, relative to the aircraft, caused by the yaw rate. This second velocity is not aligned with the chord line of the wing (it is at a significant AOA), so the vector sum effectively tilts the relative velocity vector downwards, increasing AOA.


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What is the feasibility of using drones that can fly at 360kmh as anti aircraft?
What is the feasibility of using drones that can fly at 360kmh as anti aircraft? Linked under is a similar thread. However, with the prevalence of more advanced drones such as linked below wouldn't a majority of the problems like cost and the need for large amounts be solved. Additionally, the radar footprint could be minimized and be made almost impossible to detect. I am interested in researching drones and possibly creating a paper, so please let me know if there are any other related topics.

Why aren't swarms of cheap consumer-level drones a viable anti-aircraft tactic?

What is specific about a drone, that cannot be done with a current anti-air missile?

Current anti-air missiles are extremely expensive and I was wondering how feasible these types of drones would be because 10-20~ could be manufactured for the price of one missile and could be deployed without requiring the same level of training.

Is this "drone" manually controlled? If so, it will miss the oncoming aircraft. If not manually controlled, it is simply a slower version of the current anti-air munitions.

Keep in mind, the drone in the video is only that fast because it has no excess weight. Not just no warhead, but no guidance, no IR or radar, and a bare minimum of communications and batteries - probably good for a few miles' range at most, rather than the 100+ miles needed for a practical anti-air weapon.

People have been flying 800 - 900km/h RC planes for decades. 300 is nothing special. Back in the early 2000s (I can't believe it's been 20 years!) someone in New Zealand proved that anyone can build a cheap/affordable cruise missile by building a model airplane and strapping on a pulsejet engine to it (see https://www.nzherald.co.nz/nz/boffin-builds-backyard-missile/NYAM4DESUBJZCTXHXIP2LLO32I/?c_id=1&objectid=3505296 also https://aardvark.co.nz/pjet/cruise.shtml). That thing had a speed of around 500km/h

360 km/h is far too slow to intercept an attack plane.
A cheap slow drone might be effective against a slow-flying low altitude aircraft.  Even a drunk person with a rock can disable an aircraft.

360 km/h is 200 knots, which is above the V1 for airliners. That makes it more feasible to chase an airliner on takeoff to try and get sucked into its engine, than to just hope it runs into a slow drone. However, this speed is only special for a quadcopter, fixed-wing drones could do this for decades.
It's possible that a major proliferation of drones could lead to major urban airports eventually adopting the same drone-jammers as used by military airfields. But it will probably have more to do with preventing accidents from amateur photographers than with anti-terrorism.
Reducing the RCS of a drone is not as easy as it looks. It might be small, but a single metal screw has sufficient RCS to be spotted by radar at close range, and drones also have motors and antennas. Since they are only effective during takeoff, they'll be at very close range to the airport's radar. A stealth drone will need advanced materials, shaping, and LPI electronics, making it cost as much as a missile.
In a military scenario, a more effective tactic is to load small drones with explosives and try to fly them into anything flammable. They are not effective against fast-moving targets, but aircraft on the ground make for easy targets. Drones "bird-striking" an engine is a concern in civil settings because explosives are hard to get for a civilian.

Anti aircraft payloads are 100s kg, because they need to fly long distances and considerable speed. You’re not going to shoot down a military aircraft with your 200knot drone but it could knock out a helicopter with a proficient pilot. Manually controlling the drone is a whole different issue, with no guidance it would be very difficult. The payload wouldn’t be huge and then there’s also the question of what kind of trigger/detonator you use.
Remote weapons like the RB-05a are mostly useful, but usually for stationary ground targets.


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Why use the F-35
The F-35B has been troubled by "problems with its stealth coating, sustained supersonic flight, helmet-mounted display, excessive vibration from its cannon, and even vulnerability to being hit by lightning and the US could just use AV-8Bs instead. The F-35 program costs a whopping 406.5 Billion USD and a single F-35 costs 79.2 Million USD while the AV-8B costs 23-30 Million USD which is a significantly lower price for a somewhat better aircraft. Although the AV-8B is a 50 year old aircraft it does not face the problems that the F-35B has even though it may be time to upgrade maybe the AV-8B just needs to have a new paintjob and a few upgrades.
Now I do address the fact that In terms of avionics, the F-35 truly is unparalleled. The fighter has the most advanced sensor suite of any jet in history, including the Distributed Aperture System (DAS), the Active Electronically Scanned Array (AESA) radar, Electro-Optical Targeting System (EOTS and advanced electronic warfare capabilities. But I do think we could take all of this and redesign the Harrier instead of starting from scratch and having to go through the growing pains of the F-35B.
The F-35 Lighting II is the most popular fifth-generation fighter jet in the skies today. Its technological edge and capabilities are mainly why the aircraft is so highly sought after by many countries. After all, the stealth aircraft is the most advanced fighter jet to take to the skies operationally while we could just take the stealth paint put it on a Harrier give the Harrier new engines and boom the problems are solved.

I assume you're referring to the F-35B specifically, as like the Harrier it has V/STOL capabilities.  Apart from that and being western-built and capable of ground attack, they don't really have much in common (the F-35 is supersonic, stealthy, and much more capable as a fighter, then there's the fact it's 30 year's more modern)

"while we could just take the stealth paint put it on a Harrier give the Harrier new engines and boom the problems are solved." - It doesn't work like that.

You paint your Ford station wagon red, you change the badge and boom! you get a Ferrari, problem solved

As always, with every high performance aircraft in the history of every...growing pains. Problems that will (hopefully/probably) be fixed.
The Av-8B is a 50 year old design. Time to upgrade.
Given the mindset in the question, we probably should have stopped development with the F-4 versions.

Why stop there? Why even go with the F-4 when the Panther worked well enough... Or the Hellcat...

@jwenting - I was going to say Mustang, but thats a bit of a stretch.

The design is 60 years old plus if you count the Hawker XV-6A Kestrel which first flew 7 March 1964, and was derived from the Hawker P.1127 which first flew 11 November 1960, and whose design process started in 1957, 67 years ago (in 2024).


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If pilots in a A320 or 737 had a dual engine failure, would they add flaps for the landing?
Would this not be smart to do because you may come in a little fast, therefore the flaps would send you back up? Or would you absolutely want flaps in this situation

Read up on the story of the Gimli Glider - how to fly and land a large modern passenger jet without any engines.

Flaps are controlled by hydraulic systems which are powered by the engines. No engines, no flaps. Aircraft are usually equipped with ram air turbines for this case, but they often do not provide enough power for flaps.

@jcaron: The 737 has a backup electrical extension mechanism for the flaps (although not the slats).

Flaps steepen the descent angle - in other words, you run the risk of falling short of the runway. So in a glide you keep the flaps up until you can be certain of making the landing point. Once the landing is guaranteed, you can then deploy gear as well as flap to slow down as much as possible - being aware that these actions will further reduce the gliding range, so constant reevaluation is required.

That would be up to the discretion of the flight crew, what forced landing site they selected, approach route, etc.  Typically deployment of flaps in a forced landing scenario will only be done once the airplane is guaranteed to make the landing site by gliding in that landing configuration.

You would certainly prefer to have flaps available in order to reduce landing speed. If so, the pilot in command has discretion whether using flaps is appropriate to the situation. Unfortunately, the loss of all engines may prevent flaps from being deployable. In two of the most famous airline no-engine landings I can think of, the Gimli Glider and Air Transat Flight 236, flaps could not be used due to lack of hydraulics.
In the case of US Airways Flight 1549, however, the APU was used to provide hydraulic pressure (which was impossible in the other flights mentioned, since there was no fuel left in those cases). Partial flaps were used in the ditching.

Yes flaps would be used when landing the 737 with the loss of double engine failure.  A double engine failure landing is an Emergency Procedure. Intentionally landing flaps-up with a double engine failure creates an unnessary Second Emergency.
A double engine failure flaps-up stopping distance may exceed runway length & the speed limits of the tires.
The Airbus flap system is electrical only.
The Boeing 737 flap system is normally hydraulically operated.  In the event of a Double-Engine failure, the 737 flaps can be extended electrically.
A 737 double engine failure landing is similar to a screwed-up parachute landing...there are no do-overs.

"The Airbus flap system is electrical only." -> No, it isn't: "The motors use green and blue hydraulic power for slats and yellow and green power for the flaps." (A320 FCOM - Flight Controls)

While a dual-engine failure is certainly quite the emergency, I'm not so sure about it being an Emergency Procedure.  Do you have a checklist that gives steps -- i.e. a procedure -- for such a landing in a 737?  I've done it in the sim, although not as a procedure -- you're well beyond all of our checklists if you're landing both-engines-out.  (The checklist we have for Dual Engine Failure consists of steps to get one or both restarted.)  I don't think this answer adds anything to the other answers here.


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Is Vertical Speed based on True Airspeed or Groundspeed?
I have edited this for clarity
For the same angle of descent or climb, does vertical speed increase if true airspeed is greater or if ground speed is greater (due to a tailwind)?
Imagine a triangle and assume a three degree angle of descent. The hypotenuse represents the flight path. The opposite end represents the amount of descent. The adjacent side represents the ____. Airspeed or ground speed?
If headwind matched true airspeed, I imagine an aircraft would climb and descend in place (like an elevator) without knowing anything about it's ground speed. However, with large tailwinds, ground speed will obviously be much larger. Going back to the triangle concept--the hypotenuse will be very long--which means the aircraft would descend more quickly.
Furthermore, every Captain I've talked with swears rate of descent increases with a tailwind. However, I believe this may be a result of reduced tailwinds at lower altitudes.
Do you have a source or a formula you can cite?
Thanks.

Do you want "angle" in the air, or "angle" over the ground?  Answer that, and you've answered your own question.  There are formulas out there in abundance, but this is a conceptual question, and without the solid conceptual understanding of what's going on, no formula is going to make things particularly clear.

The angle is relative to straight and level flight. I'm not sure what you're asking.

Vertical speed, as measured by the Vertical Speed Indicator (VSI) should be measured entirely by the changing air-pressure at the static port, and should be completely unrelated to airspeed and ground speed.
The static port is a small hole, (about the size of a large needle or tiny nail) in the side of the airplane, with a pressure-sensor inside.  As that sensor measures a decreasing pressure, it indicates that the airplane is climbing.
An increasing pressure indicates the airplane is descending.
Neither measurement should depend on the plane's air or ground speed.  The sensor should still work even if mounted on a hot air balloon (or other stationary craft).
Source: http://www.boldmethod.com/learn-to-fly/aircraft-systems/how-does-a-vsi-work/

I edited my question to clarify what I'm asking. This answer explains how a VSI works--which is not what I was asking.

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Does the RA (resolution Advisory) from TCAS II take into account the stall margin required?
A resolution advisory from TCAS indicates the vertical speed per minute that you must use to avoid conflict with the other traffic. Does this vertical speed given by the RA take into account the stall requirement for the aircraft?

Yes, but not directly. The TCAS is a generic box that doesn't really know anything about the aircraft performance. What it does have is a number of input discretes that allow other aircraft systems to indicate that the aircraft climb performance is limited. Other discretes code the altitude above which the aircraft cannot perform an RA climb. What drives these discretes will be unique to a specific aircraft type and defined during the STC process.
ARINC 735A TCAS Characteristic defines the following:

Climb Inhibit Discrete Input #1 through #4
  Increased Climb Inhibit Discrete Input #1 through #4
  Performance Limit Discrete Input
  Aircraft Altitude Limit Program Pins

Based on these inputs the TCAS logic will compute an RA that does not require the aircraft to climb when it is not able to safely do so.

Aircraft performance should normally suffice to execute the TCAS RA in which case you are required to do so. If you can't fully comply with the RA, get as close to it as you can whilst protecting the stall envelope. This applies even if it means acting against your ATC clearance.
In case of any conflict between TCAS, ATC and stall warning, follow:

stall warning
GPWS
TCAS
ATC

In that order of priority.

"This applies even if it means acting against your ATC clearance." Well, doesn't TCAS always overrule ATC? See the intersection of Bashkirian 2937 & DHL 611.

Yes. hence items 3 and 4

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Can I choose whether hobbyist or Part 107 rules are more advantageous when flying a UAV for fun?
According to the FAA's UAS getting started page, if I'm flying a drone for fun within a 5 statute mile radius of an airport, I need to contact the airport and any air traffic control tower before flying. As a Part 107 pilot, I can fly a drone in class G airspace up to 400 ft AGL (or over a structure) without having to contact anyone.
I have a current Part 107 remote pilot license. To me, this makes my ability to fly a drone more flexible.

If I want to fly for fun within 5 miles of an airport and the airspace is class G, I can decide I'm flying as a Part 107 remote pilot and then I don't have to contact ATC or the airport.
If I want to fly for fun within a surface non-class-G area, I can decide that I'm a flying as a hobbyist and contact ATC and the airport if I'm within the 5-mile airport radius, no airspace authorization necessary. This is a no-go if ATC says no, but otherwise a lot faster than applying to the FAA for a waiver to fly in controlled airspace.

In either case, I would ensure that I'm not anywhere near other air traffic, and that I fly safely.
When I'm flying for fun, can I pick and choose as to whether I fly as a hobbyist or a Part 107 pilot?

That's a good question. Somehow I don't think the FAA will allow you to pick and choose which regulations you're going to follow on any given day. My guess would be that since you have the license they would consider all the flying you do to be happening under that license, but that's only a guess.

Note that the privileges afforded by §101 are not so simple as to be allowed to operate within 5 miles of an airport after giving notification. §101 prohibits operating model aircraft so as to endanger the safety of the national airspace system. The FAA explicitly interprets this prohibition to include any operation over the objections of FAA air traffic or airport operators. In other words, if you were to call up an airport operator and give notification, and they objected for any reason, you would not be authorized to fly there under §101.

@JonathanWalters Correct. I should have tightened up that part of my question to include the fact that I would not continue if refused authorization. To the edit function!

Btw this question is now obsolete.  The Special Rule has been repealed -- https://www.federalregister.gov/documents/2020/12/11/2020-26726/removal-of-the-special-rule-for-model-aircraft .  In its place is now the Exception for Limited Recreational Operations https://uscode.house.gov/view.xhtml?req=granuleid:USC-prelim-title49-section44809&num=0&edition=prelim

The simple answer to your question is yes. If you meet all qualifications to fly either under §101 or §107, you may elect to operate under either part.
Any operation of civil small unmanned aircraft systems (sUAS) within the United States is subject to §107 by default. The three exceptions are air carrier operations1, hobby operation of model aircraft under §101, and operation under the provisions of a 333 exemption. This is spelled out in 14 CFR 107:

(a) Except as provided in paragraph (b) of this section, this part applies to the registration, airman certification, and operation of civil small unmanned aircraft systems within the United States.
(b) This part does not apply to the following:
(1) Air carrier operations;
(2) Any aircraft subject to the provisions of part 101 of this chapter; or
(3) Any operation that a remote pilot in command elects to conduct pursuant to an exemption issued under section 333 of Public Law 112-95, unless otherwise specified in the exemption.

Assuming that your aircraft and operation meets the applicability requirements of §101, you could elect to operate under that part. One reason for this is due to the fact that some of the applicability requirements for operating under §101 are elective. All of those applicability requirements are found in 14 CFR 101.1 and 101.41.
14 CFR 101.1 states, in pertinent part:

For purposes of this part, a model aircraft is an unmanned aircraft that is:
(i) Capable of sustained flight in the atmosphere;
(ii) Flown within visual line of sight of the person operating the aircraft; and
(iii) Flown for hobby or recreational purposes.

14 CFR 101.41 states:

This subpart prescribes rules governing the operation of a model
  aircraft (or an aircraft being developed as a model aircraft) that
  meets all of the following conditions as set forth in section 336 of
  Public Law 112-95:
(a) The aircraft is flown strictly for hobby or recreational use;
(b) The aircraft is operated in accordance with a community-based set
  of safety guidelines and within the programming of a nationwide
  community-based organization;
(c) The aircraft is limited to not more than 55 pounds unless
  otherwise certified through a design, construction, inspection, flight
  test, and operational safety program administered by a community-based
  organization;
(d) The aircraft is operated in a manner that does not interfere with
  and gives way to any manned aircraft; and
(e) When flown within 5 miles of an airport, the operator of the
  aircraft provides the airport operator and the airport air traffic
  control tower (when an air traffic facility is located at the airport)
  with prior notice of the operation.

You could elect to not fly the sUAS strictly for hobby or recreational use. Likewise, you could elect to not operate in accordance with a community-based set of safety guidelines or within the programming of a nationwide community-based organization. If you did so elect, you would then be subject to §107.

1 To my knowledge there are no air carriers operating or authorized to operate sUAS at this time. I could be mistaken. I understand that this provision prepares the way for a future with air carriers operating sUAS in accordance with other authorizations. Think Amazon delivering packages, etc.
Note: This answer does not address what it means for an aircraft to be flown strictly for hobby or recreational use. Nor does this answer address any requirements to be met in order to operate in accordance with a community-based set of safety guidelines or within the programming of a nationwide community-based organization. Nor does this answer address how the FAA will interpret the prohibition against endangering the NAS, such as if operating over the objections of FAA air traffic or airport operators. Nor does this answer address the operational requirements of §107.

According to the FAA's own FAQ, you can do either (emphasis mine):

There are two ways for recreational or hobby UAS fliers to operate in
  the National Airspace System in accordance with the law and/or FAA
  regulations. Each of the two options has specific requirements that
  the UAS operator must follow. The decision as to which option to
  follow is up to the individual operator.
Option #1. Fly in accordance with the Special Rule for Model Aircraft
  (Public Law 112-95 Section 336). Under this rule, operators must:
[...]
Option #2. Fly in accordance with the FAA's Small UAS Rule (Part 107).
  This requires operators to:
[...]

So, it's your decision. But as always, ask yourself first how you would justify that decision to the FAA if something goes wrong. As a certificated pilot, you actually have something to lose if the FAA decides to take action against you.

I feel bad that I can't accept your answer as well. I gave it to Jonathan Walters because he quoted the regs, but it was a very tough choice to make.

@Dranon No problem! It's your question, so you should pick the answer that's best for you.

I had actually asked the FAA this very question in the late summer of 2016 by email. The answer is yes, of course, and I agree with both the good answers already given.  I just wanted to add a minor point:  If you choose to fly a particular flight under Part 107 instead of Part 101, it's not enough that you're personally certified for Part 107, the aircraft you use on the flight must also be specifically registered under Part 107.


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Can I fly part 107 in DC SFRA?
I want to fly at 77° 38' and 38° 56'. This is in the DC SFRA, in class B airspace (starting at 1500ft MSL). Can I fly here as a part 107 pilot without asking permission?

If these coordinates are within a 15 mile radius of Washington National Airport, then no. If outside that radius (the SFRA) then yes. https://www.faa.gov/uas/where_to_fly/no_drone_zone/

So it's in the outer ring. So can commercial UAS fly in the outer ring?

Isn't there also a rule about notifying airports within 5 miles of your flight? Dulles International Airport is about 6 miles away from that location, so that may also be a concern.

Yah. Dulles ATC apparently won't give authorization for commercial use. https://www.faa.gov/uas/request_waiver/request_operate_controlled_airspace/

Flight by sUAS in the outer ring of the DC SFRA is permitted, and is discussed in the FAA website: https://www.faa.gov/uas/where_to_fly/no_drone_zone/
It's off topic, but I believe that there are some errors on that web page.
You may still have to ask for permission within the outer ring, depending upon other parameters of your flight.
It is noteworthy that 101 operations may not be permitted. https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_91-57A_Ch_1.pdf  near the end of the chapter.

There are two questions here.  The first question is in the thread title.  The second question is in the OP.  But they are two different questions.  It's possible the OP was edited after it was initially posted and after several answers were given.
The correct answer to the first question is yes provided the flight takes place outside the DC FRZ.
The correct answer to the second question is no because you state you are flying in Class B airspace.  Ironically it has little to do with flying in the outer ring of the DC SFRA which would otherwise be permitted.
You say you are flying in Class B.  Flying in Class B requires authorization via the FAA's dronezone portal linked here:  https://www.faa.gov/uas/request_waiver/
You may fly in Class B (or any controlled airspace) only after your online request for waiver or authorization is approved by FAA.
Don't confuse this with a Part 101 flight which has different rules.
I am posting this for anybody who might be looking for this info in a search.


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How to determine engine CG in order to calculate moments acting on it?
The aircraft has four engines mounted in pods under the wing. I know the values for the location of engine nacelle front face from the fuselage nose (longitudinal) and distance between engine centreline from fuselage centre line (lateral). I have also calculated the CG of the aircraft. The engine weight is 600kg, has nacelle diameter of 1.4m and the length of the pod is 3.5m. I do not know where and how the nacelle is attached to pylon. How do I estimate the value of Engine CG from the data provided?

Is this a homework question (which is out of scope and simple highschool math - but you also don't provide enough information to solve for the engine's CG location) or can this be answered by "ask the manufacturer" or "look at the datasheet"?

Yes this is for a homework but a long one (8 months). Since I do not have aerospace background, I am not too familiar with it. As for manufacturer, they don't have information or are not willing to share it with me. This is why I am asking for estimation or a way to assume some things. What other information do you need? If possible let me know what I should look into- any books or research papers to help me with it

Here’s one way to do it: start at the nose of the aircraft (or anywhere you like) and determine how far back each component is behind that.  Then consider the CoG which is some distance X behind the nose.  For each component you can form an expression of the form m*(d-X) where m us the mass of the component and d is the distance from the nose.  The whole expression gives the torque that the component exerts around the CoG.  If you add together the expressions for all of the components then the total should equal zero.

It’s easy then to find the value X that satisfies the equation and that’s the distance from the nose to the CoG.  You can repeat this using the vertical distance from some reference point if you want to know the vertical position of the CoG.  If your aircraft doesn’t have lateral symmetry you might need to do this a third time using spanwise offsets

@Frog Thank you! I found a CAD for it and became easier to find it by scaling it with known parameters

@itsChibi I’ll post it as an answer then, glad to be of help

Here’s one way to do it: start at the nose of the aircraft (or anywhere you like) and determine how far back each component is behind that. Then consider the CoG which is some distance X behind the nose. For each component you can form an expression of the form m*(d-X) where m us the mass of the component and d is the distance from the nose. The whole expression gives the torque that the component exerts around the CoG. If you add together the expressions for all of the components then the total should equal zero.
It’s easy then to find the value X that satisfies the equation and that’s the distance from the nose to the CoG. You can repeat this using the vertical distance from some reference point if you want to know the vertical position of the CoG. If your aircraft doesn’t have lateral symmetry you might need to do this a third time using spanwise offsets.

Isn't this how to figure the aircraft CG?  I though the question was about the engine CG...

As worded it would apply to the entire aircraft but if one includes only the engine components then it will provide the CG of the engines.

I agree that if you know the aircraft CG both with and without the engine(s) you could determine the engine CG, but despite the math being simple I'm getting a little bogged down in your explanation... (I can be a bit thick sometimes!)  So, if you know the aircraft CG and datum, and you know the distance from the datum to the front face of the nacelle, how do you determine the arm of the engine?  (presuming the CG of the engine is not the front of the nacelle.)

It’s tricky because you don’t seem to have any information from which to calculate the engine’s CG.  For a piston engine you might guess that the CG will be a little forward of the midpoint of the nacelle, for a jet maybe a little further forward.  That’s speculation based on the heavy parts of both (propeller, compressor) being located at the front.

But wasn't that the question?  @itsChibi, are you asking about how to compute the engine's effect on the aircraft CG, or how to determine the CG of the engine itself so from that you know the arm, and can then compute aircraft CG?  (I presumed the latter based on the way it's worded.)


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Russian SU-57 vs US F-22s; who would win?
Let's say that Russia acquired a full squadron of SU-57s. Who would win? So they are flown by the same cloned person and have the same training. Both fighter squadrons have the exact same ground radar feed and absolutely no difference other than aircraft.

I think this is too much speculation, there's nothing concrete in this question. Su-57 vs F-22, where? when? how?

This is completely and solely opinion based.

It is not simply Su-57 vs F-22. You have to factor in pilot training, AWACS communication, etc, etc.
Regarding pilot training...If you put an average driver in a top line F1 or NASCAR car, and put him on the grid on Sunday, competing against pro drivers that train and practice every day...your "average driver" will come in dead last, or just dead. I'd wager that USAF and USN pilots get a LOT more relevant flight hours than Russian aircrew.
Regarding AWACS, which team has the better info? USAF/NATO AWACS can vector the fighters in from farther away than the Rus equivalent.
And the ceiling of the F-22 is not 50,000 feet. Witness the shooting of the Chinese balloon, which had the F-22 at 60k feet when it launched the missile.

Let's say that they are both flown by the same clone and have the same training and wits

@VFA-34 - And still, other factors come in to play. ROE, location, missile range, other things. Everything being equal except the airframe (and it NEVER is), I give the nod to the F-22, simply due to the better stealth. See and shoot before he knows you are there.


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What's gonna be the physics behind building 'futuristic' airplanes? Use physics formulas or even theories to answer this question
After thinking about these 'futuristic' airplanes, I wonder if there's any special physics theory or law behind them. I wonder how faster they can be, persevere more and fulfill the aviation's lover wish. I would like it if someone helps me with any idea on how these 'futuristic' planes work according to Physics or even their design.

There are many possible answers to your question, so I'll give a try.
New and future aircraft are defined by the technologies that go into them.
Developing a new aircraft is very expensive, failure may risk the entire company, so we typically only take on new aircraft design when the technologies have advanced enough to make the new aircraft sufficiently better than the current ones.
Some technologies are relatively mature, so advances are slow and steady.  Others are in their early days, so we might expect breakthrough and dramatic advances.
Propulsion technologies are one of the most important to enable new generations of aircraft.  We can expect that turbofan engines will continue to get more powerful and fuel efficient -- but turbofans are very mature, so progress here will be slow.  The adoption of biofuel and sustainable fuel is one area of likely progress.  We may also shift to hydrogen as a primary fuel.
Hybrid and battery electric aircraft are an exciting new area.  Battery technology has a long way to go for most aviation missions.  Electrification opens the opportunity for a lot of design changes.  It also opens the opportunity for missions that can not be done with liquid fuel.
Other propulsion advances include high speed -- ramjet and scramjet technologies that may enable more practical supersonic and hypersonic flight.
Material technologies -- better metals, composites, and manufacturing processes.  These can enable lighter and more efficient aircraft.  They also can reduce the required maintenance on an aircraft and extend the service life by reducing the effects of fatigue and corrosion.
Aerodynamic technologies -- passive and active laminar flow, boundary layer ingestion engines, active flow control, etc.  All enable more efficient aircraft.
Autonomy -- increasing automation in the cockpit reduces pilot workload and increases safety.  Eventually this will lead to un-piloted aircraft acting autonomously.  Autonomous aircraft can do many potential missions more economically than piloted aircraft.
I'll let you continue this exercise -- think about the technology advance and then think about what it would do for aircraft design.

Why the downvote?  At least add a comment.

I think it's because opinion-based questions/answers are off-topic here

OT questions should not get answers

Note the question was after new physics, which I would have interpreted as constraining things to what is in the aerodynamics section, or possibly exotic engines.

@GremlinWranger Fair point.  I agree, after re-reading the question after my answer, there are things that could have made it a better fit.  However, (with the exception of autonomy) the examples listed often have the technologies originate in the physics.  You could argue that composites obey different physics than metals.  The physics isn't different at the level of conservation of mass, energy, and momentum -- but it is different in the details of how systems behave (turbine vs. scramjet) (batteries vs. liquid fuel) and in how we model systems (composite vs. metal).


text:
How do you communicate with atc and how can they communicate with you when you change frequency?
How do you let atc know that you are going to a different frequency and how will you be able to talk to them if they need to talk to you will they go to that frequency that you went to?

How do you let atc know that you are going to a different frequency

I can't speak about NZ-specific, but in general one of two things happen:

You ask/tell the current station you're in communication with that you wish to/are changing frequency
The station you're currently in communication with hand you off to another controller.

In the UK, this communication goes something like this:
For 1) above
G-ABCD: G-ABCD, request frequency change to [other station] [frequency]
ATC: G-ABCD squawk 7000, frequency change approved
G-ABCD: squawk 7000. G-ABCD

For 2)
ATC: G-ABCD, report your squawk to [other station] on [other frequency]
G-ABCD: Report squawk to [other frequency]

or, on reaching the limits of radar coverage.
ATC: G-ABCD you're reaching the limit of my coverage, traffic service terminates. squawk 7000, freecall [other station]
G-ABCD: squawk 7000, freecall en route. G-ABCD.

how will you be able to talk to them if they need to talk to you will they go to that frequency that you went to

Short answer: You can't and they can't. Once you're no longer on their frequency they can't talk to you.
Slightly longer answer: Occasionally, one controller is working more than one frequency. Quite often I hear something similar to 2) above (where I know from experience it's one controller working 2 radar frequencies) along the lines of "Report your squawk back to me on 125.250". In this case it's 2 radar zones, both provided by Farnborough radar - known as "Farnborough Radar North"  and "Farnborough Radar West".
Controllers at different stations can use the telephone to communicate with each to facilitate/orchestrate hand offs. I suppose if they needed to get back in contact with you, they could phone the station and ask that controller to pass you a message.

I don't have experience with New Zealand systems, only usa, but my guess is that this is the same in New Zealand as it is in America. (I could be mistaken.)
Pilot radios are designed to be user-tunable over the entire aviation frequency spectrum. ATC radios are not. Each frequency used by a facility will have its own dedicated receiver, transmitter, and antenna—and in most cases two of each, a "main" set and a "standby" set.
ATC can only select from the preset list of frequencies used at their facility—we don't have the ability to tune an arbitrary frequency, at least not on our normal equipment. We do have portable emergency radios that can be tuned to any frequency but their range is quite limited.
So to answer your second question: unless you have two radios and you can listen to both at once, ATC can only communicate with you if you remain on your assigned frequency.


text:
What navigational aid(s) would WWII bomber pilots have used while flying in instrument conditions?
In my furthering attempt to understand the accident mentioned in this post, I've become interested in how WWII Bombers would have flown on instruments.  In the accident report, the pilots states:

After passing Naknek en-route Elmendorf Field, we tried to go through Bruin Bay Pass but the Pass was closed. We climbed to about 7500 ft. and were between two layers of overcast. The layers began to converge ahead of us and before we knew it we were on instruments. Icing was severe and the antennas were lost in a very few minutes. Static was so bad on the loop antenna that the Anchorage range could not be heard. We thought our position was further East, over Cook Islet, until Co-Pilot, Lieutenant Donaldson, saw a mountain just off our wing tip and shouted to me. At almost the same instant we struck the mountain. After we got into the overcast everything seemed to happen so fast we couldn't do anything about it.

As a PPL and a budding instrument pilot, I am, of course, fairly well versed on how VORs and ADF/NDBs work.  However, It is unclear to me whether when the pilot refers to the "Anchorage range" and the "loop antenna" whether he is talking about either one of these instruments/station types.  He also mentions not being able to "hear" the range, which I would guess is similar to identifying a station with morse code the way VOR/ADF is identified today, though again, that is a guess.
Since the B-18 was much less common than the B-25 or B-17, there is much less written on them.  I did find this article, but it does not go into detail on the types of instrumentation.
I've also tried to find a decent picture of the B-18a instrument panel, but so far this one is the best I've come across:

The instrument between the compass and the turn coordinator looks a bit like an ADF, but I think the image is too fuzzy to tell for sure.
I've also seen this very informative set of answers though I don't think they answer my specific question.
So again, my question is, what navigation aid(s) would these pilots have used while flying on instruments?

Related

The accident report is referring to Radio Range navigation which predates ADF or VOR navigation.
Radio Range is used by listening to a radio tone. When the pilot is on course, he hears a steady tone. If off course to the left or right, the steady tone is replaced by a "dah dit" or "dit dah" morse code signal.
Because the antenna iced up, they were unable to hear the signal and had no directional guidance.
More info: Wikipedia Radio Range
YouTube Video: Four Course Radio Range

Tried to fix your link, for me this link: https://en.m.wikipedia.org/wiki/Low-frequency_radio_range/ was not working, but this one does: https://en.wikipedia.org/wiki/Low-frequency_radio_range.  Since my change was < 6 characters the edit failed.

Which now begs the question, "How does ice on an antenna prevent radio reception?", but that probably belongs on [electronics.se]...

Radio range didn't use a loop (= directional) antenna. That seems to be referring to early NDB rather than Radio Range.

I believe the pilot was using Radio Range because he said:  "the Anchorage range could not be heard".

what navigation aid(s) would these pilots have used while flying on
  instruments?

The short answer is the guy sitting behind them (aside from your standard 6 pack)
On planes of this size and of this era most of the navigation and operation of navigation instruments was up to the flight navigator. They sat behind the pilot and sometimes had other instrumentation back there. In many cases they had a table and a decent map as well as some stop watches a pencil and a good straight edge. The pilots were responsible for things like heading hold, altitude hold, and speed hold. Although some planes even had aft placed throttles out of reach of the pilots.

(source)
In areas of the world where NDB's and Other early radio nav ads were not really present pilotage and dead reckoning were often used. Keep in mind VOR's were not deployed until 1946.
Celestial navigation was also used however that is dependent on sky condition at the given time.
This B-29 "FiFi" Navigators station shows a pretty sparse setup of instrumentation that appears to include some kind of ADF style read out.

(Source)
This site provides a great overview of some of the nav equipment used at the time.
You can find the full 1945 "Flight Through Instruments" Naval Aviator publication here.
According to this article the B-18 did fly with a navigator

The crew, numbering three, constituted the pilot and flight navigator
  in the traditional cockpit position over the nose with the bombardier
  seated in the position at the nose proper.

Early versions were even used to train navigators,

Work began in earnest on a variant specifically for training military
  pilots, bombardiers and navigators.

the "loop antenna"

The loop antenna is a part of early ADF systems and on occasion can still be found on some aircraft (see ADF loop below).

(source)
The loop antenna is one of two components needed for an ADF system. It is the component that can detect direction. However it only has 180 degrees of precision and is ambiguous beyond that. In other words it does not know if the signal is from the front or the back. The ADF Sense antenna solves the ambiguity problem (if installed).

thanks for taking the time to answer.  Very informative stuff on flight navigators.  While I was aware of the position, I am much better educated having read your answer and links.  I suspect though based on the description of the crew and the accident that this flight didn't have a navigator.  Perhaps they were less frequent in this much quieter theater of the war?

I was answering in the slightly more general sense but I have added in some more info. It appears the B-18 was flown with a navigator.


text:
Is it better to shut down the engine(s) or leave it (them) running when a gear up landing is imminent?
Is it better to shut down the engine(s) or leave it (them) running when a gear up landing is imminent?
I noticed that the pilot in this video chose to shut down his engine before touching down during a  gear up emergency landing.  However, in Pilot Operating Handbooks, the recommendations seem to be mixed.  For example, the Cessna 210 POH, Page 3-11 says:

Touchdown -- SLIGHTLY TAIL LOW.
Mixture - - IDLE CUT-OFF.
Ignition Switch -- OFF.
Fuel On-Off Valve -- OFF (pull out).

On the other hand, the POH for the Piper Arrow III PA28R-201, Page 3-14 recommends shutting down the engine before touching down:

3.lSb Gear Up Emergency Landing (3.Sd)
  When committed to a gear up landing, CLOSE the throttle, move the
  mixture to idle cut-off, and shut OFF the ignition, battery master (BATT
  MASTR), and alternator(ALTR) switches.Turn OFF the fuel selector valve.
  Seat belts and shoulder harness should be tightened. Touchdown should
  normally be made at the lowest possible airspeed with full flaps.

What is the reason for this variation?  Is there some advantage to touching down one way vs. the other?
I've have noticed this question:

How to execute a gear up landing on aircraft with low propeller?

However, I do not believe this question duplicates that one. While consideration of the propeller would be one factor in deciding whether or not to shut down the engine, it certainly would NOT be the only one.

I would leave them on, what if you need to go around at 20 feet?

While I would follow the POH/AFM, what I was told is that shutting the engine down prevents internal engine damage due to the propeller contacting the ground under power and could save an expensive engine overhaul (in addition to the fuselage damage which will occur).

Isn't the only correct answer to follow the POH?

I just happened across This AVweb video about the subject. He makes some very good points as to why you are best leaving the engines running. The advantages to cutting them are actually pretty pointless. You're most likely not going to save your props. Fires on belly landings in ga aircraft are rare. The engines will need to be inspected anyway.

Could point #8 refer to making a PLAN for touchdown, rather than an instruction to WAIT for touchdown before proceding with later steps?  If so, that would be sloppy writing, but... ?

What variation? Both of the quoted manuals say to shut off the engine.

There's two schools of thought. First is the keep the engine on school because keeping the engine on:

Gives you more control of the airplane
Gives you the option to go around
Keeps the procedure simple and allows the pilot to concentrate on a good touchdown
Keeps the dynamics of the airplane predictable and familiar to the pilot

The shutdown the engine school's view is that shutting the engine down lowers the fire risk by cutting off the fuel and engine ignition spark.
Personally I'm with the keep the engine on school of thought. The last thing I want to be doing when I'm trying to make a smooth landing is reaching for all sorts of knobs and levers, and having to reach the fuel cutoff valve in the inconvenient places that piper likes to put them, and then learning how the airplane behaves without engine power for the first time. As soon as I touch down I am pulling the mixture, cutting off the fuel and killing the mags and the master switch, but until then I'm going to concentrate on making it the smoothest landing in the history of manned flight.

I've heard some say they shut down in an attempt to save the props... but from the plethora of youtube videos... that doesn't seem to go right most of the time.

It doesn't @SnakeDoc, it's a spectacularly bad idea. You are intentionally creating an emergency you wouldn't ordinarily dream of doing which is far more serious than the one you have.

@SnakeDoc - aren't your props going to windmill anyway?  The props won't stop moving just because the engine is off will they?

Most of the time the props will stop @DaveGremlin. That's not really the point though, it's that the distraction of bumping the props into position and the loss of power leads to crashes.

You're going to have an insurance claim anyway, since there's no escaping damages with a belly landing. Saving the props is likely the least of your worries.

Won't you still have sparks even with the engines shut down, due to (a) all the electrical wires frayed\severed in a belly landing and (b) the plane's belly scraping along the runway at high speed?

Yes there's going to be sparks either way @Sean, it'll be from the skin of the airplane, not electrical wiring. The voltages on GA airplane electrical wiring generally isn't enough to cause any sort of sparks. The wheels up landing procedure for an airplane should call for master off, fuel valve cutoff to limit the danger from the electrical system and fuel system.

@GdD: Yeah, I get that; I was more referring to the part of your post where you said "...lowers the fire risk by cutting off the fuel and spark."  (Emphasis added.)

Oh, I see @Sean, you're right that there's going to be plenty of sparks. In this case I was referring to engine spark, the amateur auto mechanic came through I guess. The thinking is that in a forced landing turning off the magnetos and cutting off the fuel supply to the engine reduces the chance of a post crash fire, which is true. However, a gear up landing is not the same thing, the instances of fire is much less, and usually fire crews are in attendance anyway.

@GdD: Even if you leave the engines on during landing, won't the scraping along the runway still produce far more sparks than the engine (plus, the sparking part of an internal-combustion engine is inside the part of the engine that's designed to essentially be on fire during normal operations)?

That would be my reasoning @Sean.

Prior military Flight Engineer, current aeronautic contractor employee here.  In the KC-10, engine shutdown on contact with ground is dictated in order to minimize potential fuel spill and fire hazard.  I would imagine that many aircraft have different procedures dictated by their design and engineering features such as landing gear and engine configuration.

The question seems to be focusing on small propeller planes, which will be a little different from the KC-10.

Actually, I had not intended to limit this to small propeller airplanes, though that is certainly where my own experience lies.

Fantastic real-world answer!

Both actions quoted result in engine off landings. Repairing a prop strike on just the motor can easily cost 1/3 the price of a motor plus a propeller. Saw a video of a guy landing gear up in a twin, he shut it down after he knew he had the runway and bumped the starters to put the props horizontal. Saved at least 40 thousand dollars doing it.

As soon as you have an emergency, the insurance company owns the plane and your only concern should be survival, not saving their plane.

I fly a low-wing, 4 engine turboprop.  We would shut down the engines by cutting off fuel, but not feather the props prior to hitting the ground.  There are several reasons for this.
1) The fire will go out in the engine, reducing the potential for fire.
2) The RPM of the prop and engine will be drastically reduced, for us it will probably drop to about 35% of normal operating RPM.  This reduces the rotational energy, and how badly the prop blades throw fragments when they hit.  On our plane the inboard props will hit before the outboards.  We also would clear personnel from any seats near the prop plane of rotation or else they're probably going to get hit.
3)  We don't feather the props because they are more likely to just bend or break off the tips if the blade angle is flat.  If they are feathered, they might tear the gearbox and engine off the plane entirely.  This is a measure to limit damage to the airframe, not really a concern about cost savings.  There is an awesome video on YouTube from the show Ice Pilots of a Lockheed Electra (very similar to my plane) landing with one of the mains up.  They followed basically the same procedure I mentioned and walked away with a lot less damage than I would have expected.

You mostly don't need to shut down fuel with aircraft with fuel tanks on the top but lets be on the safe side. This is what I would do (I Am not that great in landings):

Aircraft Cessna 172SP
Near landing means 250Meters behind the aiming point
Full flaps on near the landing
VSI is lower than HSI
Nose little bit up
Near stall speed

I Would shut down the engines and cut the mixture in order to minimize odds of getting fuel burned. Then I would try to stop on the field as fast as possible.  You will not need to shut down the engine withing 250Meters of the aiming point on aircraft with fuel tanks on the top but do that procedure as n habit.  Also you wont need engines on a properly planned landing unless you are an aircraft carrier pilot that is afraid of your tail hook not catching the arresting gear.


text:
Do long distance business jets have a crew resting area?
I am asking this question out of curiosity. Do they have separate cabin area for themselves?

Yes.  Gulfstream, FalconJet and Bombardier all offer a small crew rest space in their large cabin business jets, depending on the cabin configuration.  This isn’t similar to those found on airliners, but it does feature a normal sized and reclining seat with seatbelts, a small table, lighting, emergency oxygen and a divider for privacy from the other passengers.

The interior configuration is the choice of the operator and for most business jets is done at a separate completion center (although Bombardier does Global interiors in-house) where the interior is certified under an STC. The airplane will leave the factory "green" (no interior or paint) to go to a completion center of the purchaser's choosing.
The owner can choose to put in a crew rest area and may even include a sleeping bunk.  It'll depend on the owner's mission profile, and how that profile affects the complicated duty period regulations the operator is subjected to. They may just put in a partitioned area with a seat and amenities, or may include a full size sleeping bunk if a relief pilot is required to be on board to meet rest period regulations.

Crew rest area or compartment is a separate area of an airplane which may not be accessible to passengers. Depending on the class1 of the airplane, crew may have a rest area with isolated resting places, or a flat seat separated by a curtain or a seat which can recline and has foot support.
In the US, FAA has detailed about rest areas in 14 CFR Part 117. Accompanied by the advisory circular AC-117, the classes are:

Class 1 Rest Facility Means a bunk or other surface that allows for a flat sleeping position and is located separate from both the
flight deck and passenger cabin in an area that is
temperature-controlled, allows the flight crew member to control
light, and provides isolation from noise and disturbance.
Class 2 Rest Facility Means a seat in an aircraft cabin that allows for a flat or near flat sleeping position; is separated from
passengers by a minimum of a curtain to provide darkness and some
sound mitigation; and is reasonably free from disturbance by
passengers or flight crew members.
Class 3 Rest Facility Means a seat in an aircraft cabin or flight deck that reclines at least 40 degrees and provides leg and foot
support

The above circular also provides details about the dimensions of each class and the facilities which are required.

1: Class of an airplane depends on the number of crew and the duration of the flight.

Not sure that anything in Part 117 applies to biz jets? It certainly governs Part 121 operations, but most biz jets are Part 91 operations, or 135 if they're chartered. Does Part 117 apply to those?


text:
Engine torque due to Turbofan engines and its effect on aircraft attitude
I know that for turbofan engines there will be Gyroscopic effects while pitching, rolling and yawing maneuvre. But if the aircraft is cruising at an altitude or is simply idling on the ground, what would be the torque loads acting on the aircraft because of the rotation of fan blades? and what would be the direction of the moment if there's any?

Remember most turbofan aircraft have an even number of engines, so that with a 2-engine aircraft, each spins the opposite way, and with a 4 engines 2 spin each way.

They don't counter rotate.  All of the engines on any turbofan will spin the same direction.  The only "handing" that goes on is during the build-up to accommodate left side or right side plumbing connections.

If we are considering only one engine for analysis then yes there will be torque load which can be calculated using right hand rule which will depend on rotation of fan blades. During manoeuvre, there will be gyroscopic loads acting on the engine caused due to torque.

Are you going to accept your answer?

There is no net torque on turbofan engines
According to Newtonian physics, in order for the engine to transfer a torque onto the aircraft, it must impart some angular momentum (in the opposite direction) onto the air particles. More simply, the engine must make the exhaust gases swirl in one direction for it to transfer a torque onto the aircraft in the other direction.
However, the exhaust guide vanes exist precisely to prevent this - they ensure that the exhaust gases exit with as little angular momentum as possible. This is desirable since the EGV's are actually converting that angular momentum into linear momentum, producing some additional thrust in the process.

Image source. In this image of a GEnx, you can see the stator assembly for both the core exhaust and fan exhaust
Propeller driven aircraft do not have a stator assembly as such, and so air ends up exiting in a swirling motion, and hence the torque.

I can only read "gyroscopic" in the question. The questioner knows that there are gyroscopic effects while manoeuvring and would like to know if it exist also during stationary phases, like cruising or idling... as simple as that.

I agree anyway that the question is not clear as well as the OP-self answer.


text:
Ground speed question
A light aircraft has a landing speed of 70 knots. A wind of 25 knots is blowing over the airfield. What is the ground speed of the aircraft when it touches down, a) directly in the wind?
Why is it that this is 70-25? For the 25knots wind, is this horizontal or vertical, I think horizontal?

You’re right. It’s horizontal.  Thus 70-25.

Think of it as paddling upstream into a current. You're paddling at a running speed across the water, but because the water is moving the other way, your actual progress relative to the shoreline (or the river bottom) is more like a walking speed, as the current going against you subtracts from your water speed. If you paddle with the current, the opposite happens and you're now passing people on bicycles on the shoreline as your paddling speed is adding to the current speed. Paddle at 90 deg across the current, and it's a wash. Flying in the "air current" (the wind) is exactly the same thing.

Groundspeed can be more, or less that airspeed.  See this similar question:  https://aviation.stackexchange.com/questions/92189/how-can-ground-speed-be-higher-than-airspeed/92190#92190

Re "Why is it that this is 70-25?" - why would you think it might be otherwise?

Re "For the 25 knots wind, is this horizontal or vertical, I think horizontal?" - 25 knots is about 2500 feet per minute.  The min sink rate of a Cessna 152 w/ power at idle (in still air) is about 700 feet per minute.  So if the wind were vertical, and were upwards rather downwards, landing under such circumstances would be "interesting".  Pop quiz for you, to see if you understood the concepts behind the upvoted answer to your question - how rapidly could a Cessna 152 gain altitude with the engine at idle, without losing airspeed, under these circumstances?

PS if the wind were vertically downwards, the landing would also be "interesting", just in a different way.

Assuming, for simplicity, that the plane is landing directly into the wind:
Aircraft speeds like landing speeds, stall speeds, etc. are given in KIAS (Knots Indicated Air Speed), because so much about the airplane's operation is derived directly from how the wings are interacting with the air.
Ground speed is just the plane's movement in reference to the ground, and has no direct influence on the aircraft (the aircraft's situation determines the ground speed, the ground speed doesn't determine anything by itself).
So if the aircraft has a landing speed of 70 KIAS, that means air is going over the wings at 70 knots - that's how much air the engine is propelling the plane through. If 25 of those knots are consumed just keeping pace with the headwind, then that leaves 45 knots of forward motion relative to the ground, aka the ground speed.
This is because both the wind speed and the ground speed are measured relative to the ground.  It's just the aviator's version of the "Train A leaves station 1 at 100kph, Train B leaves station 2 on the same track in the opposite direction at 75kph, assuming both operators are asleep, at what speed do the trains collide?"

@Jim re: 4,5: Because they exist, or because they feel wrong in some way?

@Jim Edited.  I imagine you'll still be somewhat dissatisfied with the accuracy of the 4th, but it's a deliberate oversimplification for the sake of achieving illustration of the fact that you're dealing with opposed forces.

Much Better. Rescinded. :-)

They don't.  After a few minutes, the driver vigilance device kicks in and brings the train safely to a stop.

@Mark Are you trying to tell me my 5th grade math teacher lied to me?!?!?!